Fix bug : IsArgImage("true") return true instead of false.
Fix bug : IsArgImage("true") return true instead of false.

libmv/libmv,keir/libmv,petertsoi/libmv,SoylentGraham/libmv,SoylentGraham/libmv,petertsoi/libmv,rgkoo/libmv-blender,keir/libmv,rgkoo/libmv-blender,keir/libmv,Nazg-Gul/libmv,Nazg-Gul/libmv,SoylentGraham/libmv,libmv/libmv,petertsoi/libmv,Nazg-Gul/libmv,SoylentGraham/libmv,rgkoo/libmv-blender,Nazg-Gul/libmv,rgkoo/libmv-blender,libmv/libmv,keir/libmv,libmv/libmv,Nazg-Gul/libmv,rgkoo/libmv-blender,petertsoi/libmv